Postharvest Biology and Technology of Fruits, Vegetables, and Flowers

CHANGES IN NUTRITIONAL QUALITY OF FRUITS AND VEGETABLES 455
Gil et al. (1997) indicated that the treatments with CO 2 had direct effect on strawberry
anthocyanin levels. Fruits stored in air showed higher anthocyanin levels than CO 2 -treated
fruits at 5 ◦ C. A rapid decline in the anthocyanin levels was noticed with higher concentrations
of CO 2 . Fruits stored at higher CO 2 atmosphere showed a prominent decrease in the
anthocyanin content of internal tissues, whereas fruits stored in air did not show any effect
on anthocyanin levels in both internal and external fruit tissues. An increase in the pH of
internal tissues was also noticed with an increase in CO 2 concentrations, which may be the
cause of anthocyanin degradation (Gil et al., 1997). The decrease in anthocyanin concentration
at high CO 2 atmosphere (12% CO 2 ) was also monitored in sweet cherry; however,
high atmospheric CO 2 reduced the activities of PPO and POX during postharvest storage of
sweet cherries (Remòn et al., 2004). On the other hand, no changes in total phenolics and
flavonoids were found during CA storage of cranberry fruits (2, 21, and 70% O 2 with 0, 15,
and 30% CO 2 )at3 ◦ C (Gunes et al., 2002). Based on these studies, it can be concluded that
CA can have pronounced effects on metabolism of phenolics depending on the commodity.
Modified atmosphere packaging (MAP) is also used to reduce the oxygen level around
the products. Polyvinyl chloride, polyethylene terephthalate, polyethylene, and polypropylene
are the major films used in MAP. The main gases used in MAP are oxygen, nitrogen,
and carbon dioxide. Depending on the product sensitivity and color stability to these gases,
different proportions of gases are used in MAP.
MAP influences browning and PPO activity. A significant depletion in PPO activity
was observed in minimally processed “Golden Delicious” apples under MAP (90.5%
N 2 + 7% CO 2 + 2.5% O 2 and plastic pouches) (Soliva-Fortuny et al., 2001). However, no
change in color was found in ready-to-eat apples during the storage period. The selection
of atmospheric composition and packaging material significantly affects the PPO activity
and color loss in the products, and maintains the shelf life and nutritional quality of the
products. Broccoli wrapped in low-density polyethylene film lost its nutritional content
during refrigerated transportation; however, when packed with microperforated (Mi-P) or
nonperforated (No-P) films, functional compounds such as polyphenols were preserved
during storage (Serrano et al., 2006). Therefore, in general, MAP is a beneficial method to
maintain the nutritional quality and extend the shelf life of fruits and vegetables.
21.5.4 Growth regulator treatments and phenolic compounds
Fruits and vegetables are exposed to plant hormones and other chemicals to extend their
postharvest life and to maintain their nutritional contents. Several chemicals, including 1-
MCP, hexanal, methyl jasmonate (MJ), and abscisic acid (ABA), have shown their effects
on browning, phenolic compounds, and PPO and PAL activities. Loquat fruits exposed
to 1-MCP for 12 h showed lower PPO activity and browning index during storage (Cai
et al., 2006). During storage period, an increase in total phenolics was also noticed with the
decline in PPO activity in 1-MCP-treated fruits. 1-MCP-treated apples also exhibited higher
flavonoid contents as compared to control apples (MacLean et al., 2006). However, in sweet
cherry, 1-MCP treatment failed to intensify total anthocyanins and hydroxycinnamic acids,
the major polyphenols in cherries, during cold storage (Mozetič et al., 2006).
The effect of 1-MCP also depends on harvest maturity. Optimum maturity of the product
is an important factor to get the desirable effects from these postharvest treatments. 1-MCP
treatment in early-harvested apples showed less chlorogenic acid than optimal matured and